Adding and subtracting machine



Aug. 3 1926.

W. W. LASKER ADDING AND SUBTRACTING MACHINE Filed April 1, 1924 3Sheets-Sheet 1 INVENTOR William 14! [as/e1;

fiTORNE Y Aug. 3 1926.

' w. w. LASKER ADDING ANDMSUBTRACTING MACH NE Filed April 1. 1924 5Sheets-Sheet 2 INVENTOR William (Lab-Ker; BY

' 1 fi TO'RNEY Aug. 3 1926.

; w. w. LASKER ADDING AND SUBTRACTING MACHINE Filed April 1, 1924 3Sheets-Sheet 3 INVENTOR BY Wz'llz' am 14 Ana/2v:

I LTORNEY tion,

Patented. Aug. 3, 1926.

UNITED STATES .WILLIAM' W. LASKER, OF BROOKLYN, NEW

MACHINE CORPORATION, OF YORK,

YORK, Assmnon 'ro rownas ncooum'nre n. Y., a conronn'non or DELAWARE.

ADDING AND SUBTBAC'FING MACHINE.

Application filed April 1, 1924. Serial in. 703,474.

The present invention relates to computing machines which are arrangedtoperform addition and subtraction, and in connection with such machinesthe invention relates more particularly to improvements in theconstruction and operation of the carry tension mechanism.

Some of the objects of the present invention are to provide acomputing'machine in which either steps of addition or subtraction canbe performed, either being thrown into operation at will to change fromone method of calculation to the other; to pro-' vide an improved carrytension mechanism for computing machines; to provide a carry tensionmechanism which is positive and sure in operation and'in the use ofwhich it is impossible for any carry rack to carry over more than onenumber unit; to provide a carry tension mechanism having a springtension which is practically negligible in elfect upon the mainoperating lever of the machine; to provide a carry nism having asubstantially uniform spring 'tension; to provide a simple andefieetivemeans for setting the carry racks to respond to the action ofthe carry at the proper time in the cycle of operation; to provideasimple and eflicient'means for changing the operation of the machinefrom an adding function to a subtracting func tion, or vice versa, asrequired; to provide an automatic means for changing the direction ofthe applied force upon the carry tension mechanism when a change is madefrom an adding function to a subtracting funcprovements as willhereinafter appear.

In the accompanying drawings, Fig. 1 represents an elevation of one sideof a coinputing machine showing the mechanism embodying one formv of thepresent invention for causing actuation of the carry tension mechanism;Fig. 2 represents an elevation of the opposite side of themachineshowing those partshaving relation to the operation of the carry tensionmechanism; Fig. 3 represents a detail in plan of one of the carry racksand the numeral wheel operating adjuncts; Fig. 4 represents a detail inside elevation of one form of carry rack'control mechanism Fig. .5-represents a detail in side elevation of tension mechatension mechanismor vice ersa; and to provide other im:

' beheved unnecessary to describe it speclfias obviously the presentinvention only one of the carry tensionunits embodying one form of thepresent invention; Fig. 6 represents an edge elevation of the same.-

Referring to the drawings, one form of the present invention-isillustrated as applied to an adding and subtracting machine of the typeoperated by rotatable number or accumulator wheels 10,. which arearranged to be actuated by pinions 11 through engagement with indexracks 12 at certain predetermined times. stood, by reference to Fig. 3,that in the present instance one unit only of the ma- It will beunderchine is described, but inpractice there may beany number of theseunits with the accumulator wheels arranged side by side, each havingnumbers from naught to nine, so that the sequence of operation "is byway of the nine, members of the unit wheel, then a carry of one to theten'wheel, and so on with a succession of carry numbers from one wheelto the other throughout the'succession, de-

pending upon how many accumulator wheels there arein a machine. It willbe under-. stood that in this type-of machine one index rack 12 for eachpinion, and that the racks are operated through the medium there is of amain operating machine arm 13, which in the present instance connectsthrough a.

link 14 to a'main cam 15 on the main shaft 16, and from which motion istransmitted to the index racks to cause their actuation in accordancewiththe respective set positions of these racks, as determined by thesetting of the keys of the ke board of the machine. This construction fof the present invention, and it is therefore cally, requires the indexracks to be actuated at the proper time and in the proper manner for thecarrying out of the functions to which this invention relates.

. In the type of machine here illustrative of the invention, theaccumulator wheels IO 'and pinions 11 are independently mountedshaftjl'l,

orms no part, however, I

project through opposite cable cam-slides 22 and 28,- which are, mount-.5

I for free sliding movement relative to the plates 18. In the presentinstance, each of these slides 22 and 23 is provided with three of thecams 21, spaced a like distance apart for the purpose of simultaneouslyacting in pairs upon the pinion shaft designed to be controlledthereby.This provision of additional cams is made to take care of additionalpinion shafts, each of which is pro- Vided with a set of pinions andaccumulator wheels, as will be understood, so'that the machine can beequipped with one or more sets of adding and subtracting units. Innormal or rest position of the machine, the cam slides 22'and 23 are insuch a position that the cams 21 are directly beneath the rollers 20,and thereby hold the pinion shaft 17 in a position with the pinions 11out of engagement with the index racks 12. In this connection, it willbe understood that suitable spring mechanism is provided for holding thepinion shaft 17 in firm contact with the cam face of the slides 22 and23. The function, therefore, of the cam slides 22 and 23 and cams 21 isfirst to maintain the accumulator pinions 11 normally out of engagementwith the index racks 12 while determining in the operation of themachine, the time of shifting of the pinions into mesh with the indexracks 12 to roll an adding or a subtracting operation, as the case maybe. a

For the purpose of reciprocating the cam slides 22 and 23 at each addingor each subtracting stroke of the main operating arm 13, the cam slide22 is provided at one end with a recess 24, which seats about a pin 25on an arm 26, fast to a rock shaft 27, this last extending transverselyof the machine to receive on its other end a second arm 28 carrying apin 30, which seats in a recess 31 correspondingly located in the camslide 23. Thus, movement imparted to the slide 22 will be translated tothe slide 23 and the two operate in unison. To actuate the'slide 22 itis provided at one end with a trip lug 32 pivoted on a pin 33, fast tothe slide 22, the said pin33 being intermediate the tripping end of thelug 32 and a stop pin 34, which in operating position of the In 32 isarranged to abut the edge of a shou der 35 formed on the slide 22. Theopposite end of the s1ide22 carries a sim lar tri lug 36, pivoted on apin 37 on the sli e 22 and also having a stop pin 38, to abut, inoperating position of the lug, against the side face of a shoulder 40 onthe cam slide. the twolugs 32 and 36 are arran ed to be projected intooperating position y-means of a common spring 41,.which has its endsconnected respectively to the aforesaid lugs at a point to carry out thedesired operation. Where the machine is set to carry out addingoperations, one of these trip In this instance,

lugs will operate to shift the slides 22 and 23 from central position inthe correct direction to cause an adding function, and when the machineis set for subtraction, the other of the lugs will be operated to causethe slides 22 and 23 to move from central position in the correctdirection to carry out a subtracting function. In this instance, the lug32 functions for the adding operation and the lug 36.for the subtractingoperation, and selection of one lu or the other is made automatically,as will e explained. The mechanism which cooperates with the trip lugs32 and 36 consists, in the present instance, of two trip pins 42 fast tothe face of the main so spaced apart and positioned as to come into thepaths respectively of the two trip lugs 32 and 36 at the proper time andin accordance with the operation tobe carried out. Thus, if the addingtrip lug 32 is set so that it is in the path of the trip pin 42, the camslides will be shifted to the right, whereas if the trip lug 36 isselected so that it is in the path of the trip pin 43, it will beoperated, and the cam slides 22 and 23 moved to the left, as seen inFig. 2.

It will be understood that suitable restoring mechanism is provided forreturning theslides 22 and 23 to normal position after each operation;but as this mechanism forms a separate invention, it is believedunnecessary to'illustrate or describe these particular details.

For the purpose of making the selection above referred to, namely, ofpositioning the correct trip lug corresponding to the operation which isto be carried out in the ma chine, a rock bar 44 is provided, which issuitably pivoted at 45 to a fixed part, and is so arranged and locatedthat rocking movement in a clockwise direction, as shown in Fig. 2, willcause one end of the bar 44 to contact with the stop pin 34, and bymovement in a counter-clockwise direction will cause its other end toengage the stop pin 38, and whenever either end of the bar 44 picks upone of the stop pins it causes the trip lug of that stop pin to beshifted about its center to thereby remove its tripping end from thepath of the corresponding trip pin on the cam 1.5, so that when thelatter is rocked during an operation of the machine, it will fail toengage that particular trip lug. For convenience, the rock bar 44 willbe considered as a subtraction lever 46 at one end and an addition lever47 at the opposite end. The position of the rock bar 44 is, determinedby an index arm 48 secured thereto and extending to a convenientlocation adjacent the position of the operator of the machine, so thatit can be quick- 1y changed from one position to the other. This indexarm 48 is provided with a later-- and 43, both. cam 15, and.

ally disposed locking ranged to be engage normally held in engagement bymeans of a spring 52, and having three recesses 53, 54 and 55, one,53,-of which serves to lock the index arm in adding position, another,55, in subtracting position, and the intermediate one, 54, in totalposition.

In order to carry over an addition or a subtraction from one accumulatorwheel to the next succeeding wheel, carry racks 56 are employed, eachbeing operatively located with respect to the wheel pinion which it isto control. These carry rack 56 are supported and slidably guided bytransversely dis osed guide strips 57, while across the atho movementofthe respective ends of t e carry racks 56 are two movable resettingbars 58 which are arranged to be automatically operated in proper timedrelation to not only reset the carry racks 56 after a carry operationbut also to move out of the ath of the aforesaid carry racks 56 to al owthem to function. For thee-sake of clearness butone carry rack .56 withits parts comprisin one unit will behere described in detai as theseveral units are of duplicate construction. The carry rack 56 isprovided on the edge toward the numeral pinion 11 with three rack teeth60 which are located to mesh with the pinion with the pin .11 undernormal conditions, and thus serve as a lock to prevent improper movementof the wheel 10 while also providing for the necessary carry movement tothe adjacent wheel at the desired time, injeither direction.

. As a means for locking the carry rack 56 1n its normal position, it isprovided with a slot 61 opening into a locking notch 62 to receive a tabor detent 63 of a latch 64 and provide a snugseating fit so that whenthe detent 63 is in the notch 62 the carry'rack 56 is locked againstmovement in both directions. The length of the slot 61 is such that'whenthe latch detent 63 is withdrawn from the notch 62 the stroke or carrymovement of the rack is limited to a distance sufiicient only to movethe pinion 11 one tooth on its pitch line, and this is true whether therack 56 is shifted to carry an adding or a subtracting transfer.

Forv actuating the latch 64 so that the carry rack 56 is set foroperation it is pivoted at 65 to a fixed strip 66 and is normally heldby a spring 67 under tension to return and maintain the locking detent63 seated in the notch 62.- The latch 64 is provided with atrip finger68 projecting into the path of a trip 0 carried by the hub or pinion ofthe next preceding -accumulator wheel 10 and located thereon at theproper point to transfer the addition or subtraction from one wheel tothe next. This trip 7 O has an enpin 50, which is ar-' by a pivotedlatch 51 arm 80.

, with or passes through ment of the spring 84 with the hook 83, "sothat when the bar 86 swings from an firing action to the sion bar 86when a change is fromone form of calculatlon gaging face 71 on one sideto actuate the latch 64 in one direction for addition carry, and anotherengaging face 72 on the opposite side to actuate the latch 64 in theopposite direction for subtraction carry.

The carry tension mechanism, whereby the carry rack ,56 is operated orfired when released by the latch 64, consists of a' bell crank. tensionlever 76 mounted for rocking'movement on a rock'shaft fulcrum 77 andhaving a relatively long tension or firing arm 78 and a relatively shortactuating The free end of the arm 78 seats between two lugs 81 and 82fixed to the carry rack 56 and so spaced as to allow suf-. ficientclearance for the arm 78 to shift from the addition tension position tothe subtraction tension position when the carry rack 56 is locked in itsnormal position. The armterminates ina hook 83 which receives one end ofa tension 5 ring 84, the other end of which is held by a lhg 85 formedon a carry tension bar 86. This bar 86 extends transversely of themachine and is" supported at its ends by pivot pins 87, which arerotatably mounted respectively in parts of theirame 88. The pins 87 arerespectively to space the tension "bar 86 at the proper distance fromits axisof rotation and also to support the same therebetween. In thisconnection it should be noted'that the axis of rotation of this tensionthe point of attachadding position to a subtracting position there is noappreciable variation in the tension of the spring. The distance betweenthe hook Y83 and the lug 85 is such as to place a tension upon thespring suflicient to effectively fire the carry rack 56 when the latteris releasedto be subjected to the action of the o erating arm 78. Thisarrangement, while supplying the desired spring carry racks, permits aminimum tension to be used, and through the coincident-axes of thespring and carry tension bar 86, there is no added spring tensiontransmitted to the operating lev' rs during the setting of these parts.It will be noted in Fig. 5 that the above described conbar 86 iscoincident fixed to crank arms 90, which serve attachment point of thespring andthe carry rack endfof the arm 78.

For automatically shifting the carry tento the other,

to be made position by a change in the setting 0 the seposition. Thetrip the respective crank arms are provided with laterally extendingpins 91, which seat respectively in end slots 92 of the levers 93, andare oscillated as the levers 93 are rocked by movement of the shaft 77under the action of a link 94 which is fast to the shaft 77. This link94 has a pin 95 seated in a bifurcated extension 96 at one side of aslide plate 97. That is to say, at one side of the machine thereis aslidably mounted plate 97 having a bifurcated extension 96 whichstraddles a in 95 on a link 94, so that when the plate is shifted in thecycle of operations it Will cause the link 94 to rock the shaft 77 andthereby transmit motion to the levers 93 so that the carry tension bar86 with its associated parts is shifted from one position to another. Inorder to actuate the sliding plate 97 at the proper time to set themechanism which it controls, it is supported in po-- sition upon themachine frame by stud bolts 98, which traverse respectively slots 100 inthe aforesaid plate and permit the latter to have the required stroke ineither direction.

otion is transmitted to the plate 97 by means of two trips 101 and 102,both being pivoted to the plate and arranged to be shifted from oneposition to another in accordance with whether or not the machine is tooperate for an adding operation or for a subtracting operation. In thepresent instancethe two trips 101 and 102 are connected by a tensionspring 103 acting to rock the trips inwardly out of their functioning101 is arranged to control movement of the plate 97 for an addingoperation while the trip 102 is similarly arranged to control movementof the plate 97 for a subtracting operation, and selection of one tripor the other is made by a selectin lever 104 having two oppositelydisposed arms 105 and 106, one of which is arranged to engage a pin 107on the trip 101 and the other arm 106 being arranged to engage a pin 108on the trip 102. This lever 104 is pivoted at 109 to a fixed part and isconnected at 110 to a link 111 which is connected by a crank 112 on atransverse shaft 113 running to the opposite side of the machine whereacrank 114 connects by a link 115 with the selecting index arm 48. Thisselect ing lever 104 is shown in position to release the subtractiontrip 102 and the latter has therefore been thrown to operative positionby the actlon of the spring 103, so that its lower extremity is in thepath of movement of a trip pin 116 operatively located upon a rock cam117. This cam 117 also carries a second trip pin'118, which is arrangedto of the addition trip 101, so

travel in the path that when the latter is released to o erative thislecting lever 104, pin 118 will engage its trip 101' and cause the plate97 to be shiftedto a new position. The rock cam 117 is fixed to the mainshaft 16 and receives its motion in the cycle of operations during theoperation of the main control arm or lever 13.

The operation of the machine is as follows:

For adding, the index lever 48 is swung counter-clockwise from theposition, shown in Fig. 2, to a position where the locking pin 50 isseated in the recess 53 and locked by the spring controlled latch 51.This movement of the index lever 48 is transmitted directly to'thesubtraction arm 46 and the addition arm 47, and indirectly, through thelink 115, crank 114, shaft 113, crank 112, link 111, to the selectinglever 104. The action of the selecting rock bar 44 and the lecting lever104 is the same and is carried out in unison; thus the subtracting armengages the pin 38 so that its continued movement swings the trip 36about its pivot 37 out of the path of the trip pin 43, while theaddition arm 47 moves away from the pin 34 and allows the trip 32 to beswung by the s ring 41 into the path of the trip pin 42. i imultaneouslyon the opposite side of the machine the selecting lever 104 brings itsarm 106 into engagement with the pin 108 to turn the trip 102 out of thepath of the trip pin 11.6 and release the trip 101 so that it will beengaged by the trip pin 118 on the return stroke of the operating arm ofthe machine. \Vith the setting of the machine for adding, the operatorthen punches the keys for the'numbers to be added and follows this bypulling the main operating arm 13 forwardly. In consequence, the cam 15is rocked in the same direction, its trip 43 passing the trip 36 and itstrip pin 42 swinging the tri 32 out of the way to take a position to theleft of trip 32 at the end of the forward stroke of the main arm 13. Thesame operationis taking place at the opposite side of the machinebecause the main shaft 16 transmits motion to the cam 117 and causes thetrip pin 118 to take a position to the right of the trip 101. Upon thereturn stroke of the main arm 13 the respective pins 42 and 118 engagethe addition trips 32 and 101 and since these trips are prevented fromturning by reason of their pins 34 and 107 respectively abutting theedges of the cam slide 22 and the plate 97, the return rocking movementof the cam 117 causes the slide 22 and the plate .97 to move in therequired direction. The movement of the cam slide 22 slide 23.so thatthese two slides 22 and 23 operate together and cause the pinion shaft17 to ride 'down the right hand face of the cam 21 tobring the pinionsllinto mesh with the indexracks 12 t'o'roll in an adding accumulation atthe proper time in the return stroke of lever 13. The movement of theslide plate 97 is transmitted by the bifurcated extension 96 to the pin95 on the consequentl racks is released and the firin next succeedingnumber of the site direction to whichthey did on the 'tion operation. Byreference to 1, it

link 94 so that the latter is rocked to trans mit this motion to therock shaft 77 which through the levers 93 swings the carry tension bar86 to the adding position. This shiftin of the bar 86 changes thedirection of pulf of the carr tension spring 84 and trans ers thepressure of the firing arm 8 from the lug 81 to the lug 82 so that whenthe carry rack 56 is released it will be fired in the required directionto erform a carry operation. The foregoing adding operation takes placeon the return stroke of the main lever 13, during the first part ofwhich the pinions 11 roll in an adding accumulation and tripping suchcarry racks, as are to be set, by a fractional amount and before thereturn stroke is completed the resetting mechanism for control ing thecarry arm 78 fires the set carry racks to allow ful carry to take place.When this happens, the cam slides 22 and 23 have been returned to theirnormal position with the earns 21 raising the pinions 11 out of meshwith the index racks 12 and in mesh with the teeth 60 of the carryracks56 so that the motion of the fired carry racks turns the accumulatorpinions a distance equal to one tooth and thus brings the requiredaccumulator wheel into indicating ositio'n. In this connection it shouldbe note that it is impossible for the firing movement of the carry rackto overthrow because it has a positive lock stopthrough engagement withthe carry pawl tab 63. This prevents a carry of more than one unit ateach carry operation.

For subtraction, the index, lever 48 is swung clockwise to the position,shown in Fig. 2, where the pin 50 is seated in the recess 55 and lockedbythe spring control latch 51. This movement of the index lever 48 istransmittpd directly to the arms 46 and 47, and indirectly, by way oflink 115 and shaft 113 to the "link 111 of the selecting lever 104. Theresulting movement of the lever 48 is to cause the addition tri 32 to beraised and held out of the path of the .pin 42 on the return stroke ofthe latter, and-to drop the trip 36 into the "ath of thepin 43 on theforward stroke of the latter. Therefore, as the cam 15 movescounter-clockwise on the fonwardstroke of the mainoperating lever 13 thepin 43 will engage the trip 36 and transmit motion to the connec'tgd camslides 22 and 23 to cause them to mo in the oppoaddiwill be seen bythis'o peration that t e cam slide 23 moves downwardly to the rlght, and

' thus allows the accumulator shaft 17 to ride down the upper-side ofthe cams 21 so that "the index racks 12 engage the pinions 11 to roll ina subtracting operation on the forward stroke.

Following this rolling out of the subtraction operation the continuedforward pull of the main operating lever 13 will cause the cam 117 toreach the position where the pin 116 engages the trip 102 and thereforetransmits its -motion to the slide plate 97 and move the latterdownwardly to the right,

as shown in Fig. 1, thus actu tension mechanism, including the link 94,rock shaft 77,

ating the carry pin 95, so that the carry tension bar 86 is swungcounter-clockwise to substraction position. During this swinging of thetension bar 86 the the tension spring 84 direction of pull of will bechanged and result in shiftingthe firing arm 78 away 80 from lug 82 andinto 81, and places the carry me a to carry in the o it bid for thedition enga ement with lug under tension posite direction from whichcarry. On the return stroke of the main lever 13 the cam slides 22 and23 are automatically returned to their normal position, and ion shaftcams 21 and brings 17 rides back to the trap consequently the pinof thethe aforesai pinions again into mesh with the carry racks 56.

When the main operating lever 13 has reached a oint just return stro e,the their control latch ation are released by before the end of itscarry racks which have es set for a carrying opera fractional amount,

which insures the latches against return to the locking notches prior tothe carry operation, and

a continuation of the return movement finally releases the resettingmechanism controlling these carry racks so that the said racks aresubtraction, are fired tion from which they ing carry operation free tobe fired by the tension or firing arms 78. These, of course,

for the in the opposite direcwere during the add- It will be noted that10;

upon this return stroke of the operating lever 13 the cams 15 and 117carry their pins 42 and 118 respectively past the addi- -tion trips 32and 101, because these latter are held out of the way through'thepositioning of the selecting arms '44 an Thus, for a subtracting 43 and116 are the ones the respective parts 6. 104. operation, cam insfunctioning to s ift controlled thereby,

while upon an adding operation the pins 42 and 118 become the 0 movingthe respective direction.

It will now be app unitary carr tension racks of ad ing and peratingpins for parts in the opposite arent that a complete mechanism for carry120 subtracting machines has been devised, wherein the heretoforecomplex mechanism been greatly simplifie for this purpose has (1 and thenumber of parts very materially reduced. This simpli- 12 fication of thecarry tension mechanism 'results also in raising the percentage ofdurabilit and certainty pare to carr fore used WhlOl'l emp tensionmechanisms of operation, as comhereto-. loy a multiplicity of connectedto the other ng machines comprisin parts, ;;incl uding pawls, springs,detents, and the like. In the present invention all such trains ofmechanisms have been eliminated with the result that defects due to thepresence of the elements of such mechanisms are done awa with. It shouldalso be noted that the simplified carry tension mechanism of the presentinvention is common to both addition and subtraction carry operationsand has therefore disposed of all parts which have been commonly broughtinto use for a subtraction carry in place of other parts employed duringaddition carry. Thus the present invention does away with expensive,complicated and burdensome parts which havc been in long use and whichthe industry to which this invention pertains has found heretofore nomethod of dispensing with.

Although but one form is shown in which this invention maybe embodied,it is to be.

understood that the invention is not limited to any specificconstruction, but might be applied in various forms without departingfrom the spirit of the invention or the scope of the appended claims.

Having thus described my invention, I claim: I

1. A mechanism for adding and subtracting machines comprising areciprocal carry rack, an accumulator wheel arranged to be moved to meshwith said rack, a tension spring, a firing member connected to one endof said spring and arranged to hold said car ry rack under tension, afulcrum for said member located between said sprin connection and thecarry rack end of sai mem: her, ,and means connected to the other end ofsaid spring for changing the direction of the applied tension'of saidspring whereby the direction of carry of said carry rack can bereversed.

2. A mechanism for adding and subtrafzting machines comprising areciprocal carry rack, an accumulator w eel arranged to be moved to meshwith said rack, a tension spring, a firing member-connected to one endof said 5 ring and arranged to hold said carry rac under firin tension,afulcrum or said member located between said spring connection: andthe-rack end of said firing member, and means including a pivoted armend of said spring for changing the direction of the appliedtension ofsaid spring whereby the firing direction of said member isreversed tochange from one form of carry tothe other.

3. A mechanism for adding and subtracta reciprocal carry rack, anaccumulator w eel arranged to be moved to mesh with said rack a tensionspring, a firing member connected to one end of said spring and arrangedto. hold said carry rac under firin tension, a fulcrum for said memberlocated spring connected to shift said between said spring connectionand the rack end of said firing member, and means including an armpivoted on an axis coincident with the member end of said spring forchanging the direc tion of the applied tension of said spring, wherebythe firing direction of said member is reversed to change from one formof carry to the other.

4. A carry tension mechanism for adding and subtracting machinescomprising a carry rack mounted to move in a direction for additioncarry and in a direction for subtraction carry, a firing member arrangedto cooperate with said carry rack, a tension spring connected tosaid'member, means holding said spring under constant tension, means forswinging said spring and holding means about the spring connection withsaid member as an axis to change the direction of the applied tension, aselecting device for setting said swinging means for a prede terminedcarry operation, means actuated. at a predetermined timein said machinefor causing said swinging means to function, and means for locking saidselecting device in set position to retain the operation ofing all theselected operation.

5. A carry tension mechanism for adding and subtracting machinescomprising a carry rack mounted to move in a direction for additioncarry and in a direction for subtraction carry, a firing member arrangedto cooperate with said carry rack, a tension to said member, meansholding said spring under constant tension, means for swinging saidspring and holding means about the spring connection with said memberas-an axisto change the direction of the applied tension, a selectingdevice for setting said swinging means for an addition carry, and meansactuated at a predetermined time in the addition stroke of said machinefor causing said swinging means tofunction to shift said spring andholding means from subtracting carry position to carry position. carrytension mechanism for adding and subtracting machines comprising a carryrack mounted to move in a direction in a direction for for additioncarry and subtraction carry, a firing member arranged to cooperate withsaid carry rack, a tension spring connected to 'said member, meansholding said spring under constant tension, means for swinging saidspring and holding means about the spring connection with said member asan axis to change the direction of the applied tension, a selectingdevice for setting said swinging means for an addition carry, meansactuated at a predetermined time in the addition stroke of said machinefor causing said swinging means to function spring and holding meansfrom subtracting carry position to adding. carry position, and means forlocking said tension spring means for all successive additionoperations.

7. In an adding and subtracting machine, the combination of accumulatorwheels, a common mechanism for controlling addition and subtraction, acarry rack, a latch arranged to lock said carry rack in a centralposition, means to automatically release said latch, a pivoted carrytension means for firing said carry rack, means to intially release Isaid carry rack to set said carry rack for a the combination ofaccumulaton wheels, a

common mechanism for controlling addition and subtraction, a carry rack,a latch arranged to lock said carry rack in a central osition, means toautomatically release said atch, a pivoted carry tension means forfiring said carry rack, means to initially release said carry rack tofor a carry operation, means operating at the same side of the fulcrumof said carry tension for; reversing the action of said carry tenslonupon sa d carry rack, and means for maintaining a substantially constanttension set said carry rack v on said carry tension means when shiftingsaid tension means from one form of carry to the other.

Signed at Philadelphia, county delphia, State of Pennsylvania, day ofMarch, 1924.

this 18th WILLIAM W. LASKERQ of Phila-

